Three American hospital workers for a Christian charity, among them a father and a son, were shot dead by an Afghan security guard on Thursday in Kabul. The suspected killer shot himself but survived and is currently in custody, officials said.

CURE International and the U.S. embassy confirmed the deaths.

"We are grieved to confirm, as has already widely been reported, the CURE Hospital in Kabul, Afghanistan, was the site of a shooting this morning. Three individuals, including a doctor who served at the hospital, were killed, and two others were injured," the Christian nonprofit said in a statement.

The attack outside the CURE Hospital, which specializes in maternity and pediatric care, occurred without warning, according to reports. The security guard, a member of the Afghan Police Protection Force assigned to the hospital, reportedly opened fire on the Americans as they walked by outside.

The security guard was treated at the CURE Hospital after shooting himself and is now in the custody of the Afghanistan government, according to CURE.

Health Minister Suriya Dalil condemned the attack on the hospital, which is considered one of the leading medical facilities in Afghanistan.

"They were not the people carrying guns, they did not have military uniforms, they came here under immense pressure and were here only to serve the people of Afghanistan," Dalil said.

"This was an inhumane and brutal action, and unfortunately will impact our health services."

The Christian organization opened the hospital in Kabul in 2005 at the invitation of the Afghan government. Twenty-seven doctors and 64 nurses work at the facility where 37,000 patients a year are served. According to its website, CURE's first hospital was opened in Kenya in 1998, and since then the organization has treated over 2.1 million patients, provided over 150,000 surgeries and trained over 6,600 medical professionals.

CURE said it remains committed to serving the Afghan people despite the attack.

"Please join us in praying for the families of the victims and those affected by the shooting as well as the ongoing peace of Afghanistan," the nonprofit stated.

The Taliban has claimed responsibility for a number of attacks against foreigners in recent months, though it has not yet commented on the latest shooting.

Two Associated Press journalists were shot in Afghanistan's eastern Khost province on April 4, resulting in the death of German photographer Anja Niedringhaus.

Last month, Taliban fighters set off a deadly car bomb and stormed a guest house in Kabul, where they held a number of foreign hostages, including three Americans. And in January, eight Afghans and 13 foreigners were killed by a Taliban suicide bomber and gunmen who attacked a restaurant in Kabul.